Exhaust gas purification filter

Abstract

An exhaust gas filter is capable of suppressing the generation of an excessive pressure loss due to the particulates deposited. At least a part of a multiplicity of cells surrounded by partitioning walls of the honeycombed exhaust gas purification filter have plugs on one of their two end portions. At least a part of the cells to be arranged on the downstream side in the fluid path are partial plugs having openings allowing the fluid flow. The pressure loss caused when the fluid entering the cells passes through the partitioning walls is smaller than the pressure loss caused when the exhaust gas passes through the partial plugs.

What is claimed is:  
     
       1. An exhaust gas purification filter of a honeycombed structure having a multiplicity of cells surrounded by partitioning walls, 
       wherein at least some of the cells each have a plug at one of the end portions thereof,  
       wherein at least some of the plugs to be arranged on the downstream side of the honeycombed structure in the fluid path are partial plugs each having an opening allowing the fluid to pass therethrough, and  
       wherein the pressure loss caused when the fluid entering the cells passes through the partitioning walls is smaller than the pressure loss caused when the fluid passes through the partial plugs;  
       wherein each of the end surfaces of the exhaust gas purification filter includes an alternate arrangement of the cell end portions each having a plug and the cell end portions each having no plug; and  
       wherein all the plugs located on the upstream side of the honeycombed structure are full-fledged plugs capable of blocking the passage of the fluid entirely.  
     
     
       2. An exhaust gas purification filter according to  claim 1 , 
       wherein the filling rate of said partial plugs is in the range of 5 to 80% in terms of ((A−B)/A)×100, where B is the area of the opening of each partial plug and A is the area of the cell opening.  
     
     
       3. An exhaust gas purification filter according to  claim 1 , 
       wherein the plugs located at the central portion of the downstream end surface of the exhaust gas purification filter are partial plugs, and the plugs located around the partial plugs are complete plugs or completely blocking the passage of the fluid.  
     
     
       4. An exhaust gas purification filter according to  claim 1 , 
       wherein all the plugs located on the downstream end surface of said exhaust gas purification filter are the partial plugs.  
     
     
       5. An exhaust gas purification filter according to  claim 1 , 
       wherein the partial plugs represent at least 30% of all the plugs located on the downstream end surface of said exhaust gas purification filter.  
     
     
       6. An exhaust gas purification filter according to  claim 1  wherein the exhaust gas purification filter is made of ceramic. 
     
     
       7. An exhaust gas purification filter 
       of a honeycombed structure having a multiplicity of cells surrounded by partitioning walls,  
       wherein at least some of the cells each having a plug at one of the end portions thereof,  
       wherein at least some of the plugs to be arranged on the downstream side of the honeycombed structure in the fluid path are partial plugs each having an opening allowing the fluid to pass thererough,  
       wherein the pressure loss caused when the fluid entering the cells passes through the partitioning walls is smaller than the pressure loss caused when the fluid passes through the partial plugs; and  
       wherein that area of the downstream end surface of said exhaust gas purification filter which is located within a curved line connecting the middle points of the lines connecting the center and the outer periphery of the downstream end surface is defined as a central area, and the area located outside the particular curved line is defined as a outer peripheral area, and  
       wherein the partial plugs represent a higher percentage of the plugs in the central area than in the outer peripheral area.  
     
     
       8. An exhaust gas purification filter comprising: 
       a honeycombed structure having a multiplicity of cells surrounded by partitioning walls thereby defining longitudinal passages from an upstream to a downstream end of said structure;  
       solid complete plugs being disposed in the upstream end of a first subset of said passages so as to prevent direct gas flow into the upstream ends of said first set of passages; and  
       plugs also being disposed in the downstream end of the remaining subset of said passages wherein at least a substantial portion of the plugs in said remaining subset of passages are partially open plugs such that the pressure drop experienced by gas flowing through the filter from the upstream end to the downstream end is limited even in the presence of excessive particulate deposits along said passages.  
     
     
       9. An exhaust gas purification filter as in  claim 8  wherein said structure is made of ceramic. 
     
     
       10. An exhaust gas purification filter as in  claim 8  wherein the partial plugs have an effectively plugged area in the range of 5% to 80% in terms of ((A−B)/A)×100 where B is the area of the opening in the partial plug and A is the cross-sectional area of the passage being partially plugged.